Essential Insights On The Evans Calcaneal Osteotomy

Pages: 58 - 64
Author(s): 
Kieran T. Mahan, DPM, and Rachel Tuer, DPM

The Evans calcaneal osteotomy has become a primary surgical treatment for both adults and children with pes plano valgus as it offers fewer complication rates in comparison to other procedures. These authors provide step-by-step surgical pearls as well as a guide to managing patients postoperatively.

   The flexible pes plano valgus deformity is a difficult problem to evaluate, classify and treat. There are a number of different approaches to the surgical evaluation of the pes valgus foot. One of the most straightforward approaches is to view the foot as two columns.

   Evans first introduced the idea of medial and lateral column imbalance, as it applied to talipes equinovarus, in 1961. In this case, he described the lateral column as long in comparison to the medial column. Evans popularized the shortening of the lateral column to compensate for this imbalance with a calcaneocuboid fusion.

   The advent of the Evans calcaneal osteotomy is rather similar to the discovery of penicillin as both were a result of some lab or medical misadventure. After performing a lateral subtraction osteotomy in a residual clubfoot that resulted in a post-op complication of pes plano valgus deformity, Evans performed calcaneal lengthening to correct the complication. He reported the procedure in the orthopedic literature in 1975 but Ganley popularized it in the podiatric field a few years later.1

   The Evans osteotomy is an anterior beak osteotomy of the calcaneus with bone graft lengthening. It offers triplanar correction of symptomatic flexible flatfoot by adducting and plantarflexing the forefoot, and supinating the subtalar joint.2

   The procedure has evolved over the decades and become one of the primary surgical treatments of pediatric and adult flatfoot deformities. When the surgeon uses it appropriately, the Evans offers triplanar correction of pes plano valgus deformity with a lower rate of complications than some other procedures. Interestingly, Evans first described the osteotomy for a rigid flatfoot. Today surgeons use it much more commonly for flexible flatfoot with rigidity actually being a relative contraindication.

What You Should Know About Clinical Presentation And Evaluation

   A symptomatic pes plano valgus deformity often includes complaints of medial arch pain, medial ankle pain, radiating leg pain, generalized leg fatigue and even lateral impingement pain as the deformity progresses. Activity may aggravate pain, which usually prevents the patient from participating in athletic sports or recreation.

   In some cases, adolescent or adult patients have developed a sedentary lifestyle and activity brings on foot pain. Patients who become sedentary due to foot pain may have an associated weight gain, which exacerbates the symptoms. An adult patient may complain more of a progressive deformity while the pediatric patient cannot recall a time when the foot looked “normal.”

   Clinical examination should include both static and gait evaluations. On static stance, the patient may have the “too many toes” sign, loss of the medial arch, prominence of the talar head and eversion of the calcaneus. The arch should return with the Hubscher maneuver if the deformity is flexible. All or most of these findings may disappear in the unloaded foot due to the flexibility of the deformity. In the unloaded foot, one should evaluate the tightness of the gastrocsoleal complex with the knee flexed and extended.

   In gait, there is commonly an early heel-off, abduction of the forefoot and loss of the medial arch with weightbearing on the navicular or talus.3 Both children and adults, but more likely adults, may have trouble with maintaining balance on their toes or doing a double or single heel rise. It is important to evaluate the strength of the posterior tibial tendon, especially when it comes to the adult-acquired deformity. The Evans procedure reduces the stress on the medial column. Accordingly, it is a procedure for both pediatric and adult-acquired flatfoot deformities.4 One should also assess the more proximal structures, such as knee valgus, external rotation at the hip and limb length discrepancies.

   Radiographic examination should include weightbearing anterior-posterior (AP), lateral and medial oblique foot films. Ankle films can rule out any primary valgus deformity at this joint. Subtalar joint neutral radiographs may also be helpful in unmasking a subtle metatarsus adductus deformity. Bear in mind that the Evans osteotomy can exacerbate an unrecognized metadductus deformity and cause new postoperative symptomatolog.5

   On the weightbearing AP view, findings include an increased calcaneocuboid abduction angle, increased talocalcaneal gapping and decreased talonavicular articulation. An increase in Meary’s angle, a decrease in talar declination and a decrease in calcaneal inclination angles will be visible on the lateral view. The surgeon can use the medial oblique view to assess the joint space and articulations. One can also use the films to assess the bone stock and maturity of the calcaneus.

What Are The Contraindications Of The Procedure?

   Surgeons should postpone the Evans in patients with an immature calcaneus, which usually matures at about age 10. If the deformity is rigid and nonreducible, then the Evans may not be the best procedure. Computed tomography (CT) or magnetic resonance imaging (MRI) may be indicated to assess for tarsal coalition or arthritic adaptation.

   Although a tarsal coalition is not an absolute contraindication to the Evans procedure, one should resect the coalition and evaluate the joints for reducibility prior to performing an Evans calcaneal osteotomy. Metatarsus adductus and arthritis of the calcaneocuboid joint may be exaggerated or exacerbated by the Evans. Social factors, such as an inability to comply with the postoperative course, may also prevent the surgeon from performing the Evans calcaneal osteotomy.

What To Consider Before Attempting Surgery

   A clinician who is considering performing the Evans calcaneal osteotomy should first attempt conservative treatment. Conservative treatments include stretching of the triceps surae, orthoses and weight loss in the patient with an increased body mass index. Attempting these measures also allows the clinician to determine the ability of the patient to comply with a postoperative course.

   If the patient does not have relief of symptoms with conservative therapies, it is time to progress along the algorithm to discussing surgical intervention. One should plan surgery to address the particular deformity of the patient. Surgical options may include an Evans calcaneal osteotomy and various ancillary procedures.

   Many patients will require a gastrocnemius recession/ lengthening or a tendo-Achilles lengthening (TAL). One of these procedures is often an adjunct to the Evans due to the loss of 5 to 15 degrees of ankle dorsiflexion from the Evans procedure itself.6 Usually, a medial column plantarflexory procedure or augmentation of the soft tissues of the medial column is necessary. In some patients, a medial displacement osteotomy of the calcaneus is also necessary. If you are planning medial work, it is preferable to place the Evans graft after the medial procedures in order to reduce the likelihood of dislodging the Evans graft.

   The typical order of procedures in a flatfoot reconstruction would be as follows:

   • TAL;
   • dissection and Evans calcaneal osteotomy;
   • Cotton osteotomy and/or medial arch suspension (and flexor digitorum longus augmentation to the posterior tibial tendon in the adult);
   • placement of appropriately sized grafts for Evans and Cotton osteotomies; and
   • closure.

   The order of the procedures is important and the surgeon must assess the need for the next procedure sequentially throughout the surgery.

A Step-By-Step Guide To Operative Technique

   The surgeon performs the Evans procedure with the patient in the supine position with a bump under the hip of the ipsilateral side. During surgical scrub and preparation of the leg, take care to maintain the internal rotation of the hip provided by the bump. Identify and mark the anterior beak of the calcaneus, sinus tarsi, calcaneocuboid joint, fifth metatarsal base, peroneals and sural and intermediate dorsal cutaneous nerve locations.

   Make an oblique incision, oriented within the relaxed skin tension lines, just proximal to the calcaneocuboid joint and 1 cm below the tip of the fibula. Take care to avoid the intermediate dorsal cutaneous and sural nerves. One may use a Crego periosteal elevator to protect and retract the peroneal tendons. The muscle belly of the extensor digitorum brevis should be readily visible within the incision and can be reflected from its origin with an L-shaped incision that extends directly onto the calcaneus. The surgeon can reapproximate this muscle belly to its origin after the osteotomy and graft placement so leave a small tag at the origin.

   Using a blunt retractor, continue dissection and exposure with the release of dorsal and plantar soft tissue from the planned osteotomy site. Take care not to disrupt the medial structures. A minimal release of the plantar tissue preserves the long plantar ligament and may improve the correction provided by the Evans by increasing the tension in the plantar lateral arch.

   The surgeon should carefully avoid violation of the calcaneocuboid joint in order to preserve the ligamentous attachments and prevent hypermobility of the distal segment after the cut. The osteotomy is usually 1 to 1.2 cm proximal to the calcaneocuboid joint, which is usually just as the anterior beak begins to flare downward. Placing the osteotomy more proximally, such as at 1.5 cm, is more likely to injure the medial structures. In particular, be sure to avoid the middle facet.

   Perform a through and through osteotomy with a sagittal saw, using a light touch when breaching the medial cortex. Aim the saw slightly anteriorly in order to facilitate the distraction of the osteotomy and reduce the risk of hitting any vital structures. The typical bunion blade may not be long enough in the larger patient to reach the medial cortex. In this case, one may use an osteotome. A larger saw blade makes this cut faster and easier, but does require extra attentiveness to the medial structures.

   Insert a thin osteotome into the completed osteotomy and pry it open. Place the leverage on the distal fragment as that should move more easily than the proximal fragment. Another way to distract the osteotomy site is with two K-wires or a Hintermann retractor, although this is usually unnecessary. Then insert a lamina spreader into the osteotomy site. Place a hand on the talonavicular articulation at this point to assess its congruity while slowly widening the osteotomy.

   The next decision that the surgeon must make is how much distraction is necessary. While palpating the talonavicular congruity, observe the adduction and plantarflexion of the forefoot. When there is slight improvement in the forefoot and good talonavicular congruity, one may lock the lamina spreader into position. It is also easier to orient the lamina spreader at one end of the osteotomy instead of in the middle so one can place the graft.

   Cut the graft into a trapezoidal shape with the base oriented laterally. Orient the cortical bone superiorly, inferiorly and laterally in the osteotomy site. This is a lengthening, not a wedge osteotomy. A triangular graft is not as effective as a truncated wedge or rectangular graft.

   One may use various types of bone graft, such as autogenous graft, allograft, xenograft or synthetic graft. In general, iliac crest allogenic bone is a very effective choice for the Evans. In a revisional surgery, autogenous graft may be preferable. Other good choices for revisional surgery include demineralized bone matrix or allogenic bone graft with the addition of bone marrow aspirate to provide growth factors.

   Some patients may be opposed to using cadaver bone for various reasons. For these patients, one may explore the use of bovine graft or synthetic graft. Consider the osteoconductivity, osteoinductivity and strength of the graft when choosing any graft. In a graft with less strength than a tricortical iliac crest, the surgeon should consider adjunct fixation.

   One alteration the senior author has made over the years is the size of the graft. Rather than placing a graft that is 10 to 12 mm at its base, the senior author obtains adequate correction from smaller grafts at 6 to 7 mm. The graft tapers to about two-thirds of the lateral wedge. A decrease in calcaneocuboid arthritis and peroneal spasm might be expected from a smaller graft, but the more noticeable difference is the decreased incidence of subtalar joint jamming with the decreased graft size.

   Dinucci observed that grafts larger than 6 mm may compromise the long plantar ligament without providing additional correction.7 Fixation of the graft is not usually required as the calcaneus provides enough compression on the graft. If the graft does tend to pop dorsally or plantarly, the senior author finds it effective to use a smooth K-wire through the anterior beak, graft and into the calcaneus. One can pull this at a later time. The surgeon may use a small plate or screw from the cuboid to the calcaneus.

   For the senior author, the risk of calcaneocuboid arthritis outweighs the benefits of fixation for most patients. A layered closure with absorbable suture and a subcuticular stitch usually leaves a cosmetically pleasing scar, particularly with placement of the oblique incision in the relaxed skin tension lines.

Pointers On Postoperative Care And Managing Complications

   Place the patient in a non-weightbearing short leg cast with the ankle at 90 degrees for six to eight weeks. One should monitor the incorporation of the graft every two to three weeks via a radiographic exam. After you have obtained more than 50 percent incorporation, you may allow the patient to transition to weightbearing in a removable cast boot.

   The patient’s goal is usually to improve the clinical symptoms whereas the surgeon’s endpoint is often to normalize more objective measurements like radiographic angles. The surgeon must commit to following and treating the patient until the presenting symptoms resolve. One should also ensure the patient and family members are well informed regarding the postoperative course and its importance.

   Complications do occur with the Evans but one can manage these without a revisional surgery in many cases. Some of the more frequent complications include calcaneocuboid arthritis, bone nonunion, over- or undercorrection of the deformity, peroneal spasm or subtalar joint jamming. In the event that there is an inadvertent cutting of a peroneal tendon, one may use a non-absorbable suture such as Ethibond (Ethicon) for a primary repair.

   Addressing the complications early is more beneficial than ignoring them. A slow healing osteotomy, for example, may benefit from a bone stimulator early on to avoid a nonunion. Calcaneocuboid arthritis may benefit from an orthotic with a spring plate. This adds stiffness to the orthotic and helps reduce motion of the joint. Other complications may require a second trip to the operating room.

In Conclusion

   The first line of treatment for flexible pediatric or adult flatfoot is control of the unwanted pronatory motion and hypermobility using an orthotic or brace. One should put into place a strict regimen of stretching the tendo-Achilles.

   If conservative treatment fails, the clinician may consider surgery, specifically an Evans calcaneal osteotomy. The Evans lengthens the lateral column of the foot, which supinates the subtalar joint, plantarflexes the midtarsal joint and adducts the forefoot. Intraoperatively, the use of a smaller graft, placement of the graft at the appropriate level and anatomic dissection has made the procedure more successful in our experience.

Dr. Mahan is a Professor and Chair of the Department of Podiatric Surgery at the Temple University School of Podiatric Medicine in Philadelphia.

Dr. Tuer is the Chief Resident of Podiatric Surgery with the Temple University Hospital Residency Program.

For further reading, see “Key Pearls Of Calcaneal Osteotomies” in the May 2003 issue of Podiatry Today.

To access the archives or get information on reprints, visit www.podiatrytoday.com.




References:

1. Evans D. Calcaneovalgus deformity. JBJS Br 1975; 57(3):270-278.
2. Sangeorzan BJ, Mosca V, Hansen Jr ST. Effect of calcaneal lengthening on relationships among the hindfoot, midfoot and forefoot. Foot Ankle 1993; 14(3):136–41.
3. Labovitz JM. The algorithmic approach to the pediatric flexible pes plano valgus deformity. Clin Podiatr Med Surg 2006; 23(1):57-76, viii.
4. Arangio GA, Chopra VC, Voloshim A, Salathe E. A biomechanical analysis of the effect of lateral column lengthening calcaneal osteotomy on the flat foot. Clin Biomech 2007; 22(4):472–477.
5. Mahan KT, McGlamry ED. Evans calcaneal osteotomy for flexible pes valgus deformity. Clin Podiatr Med Surg 1987;4(1):137–51.
6. DeYoe B, Wood J. The Evans calcaneal osteotomy. Clin Podiatr Med Surg 2005; 22(2):265-76.
7. Dinucci JR, Christensen JC, Dinucci KA. Biomechanical consequences of lateral column lengthening of the calcaneus. Part I: long plantar ligament strain. J Foot Ankle Surg 2004; 43(1):10–15.
Additional References
8. Brostrom MPG and Seigerman DA. The clinical use of allografts, demineralized bone matrices, synthetic bone graft substitutes and osteoinductive growth factors: a survey study. HSS J. 2005 September; 1(1):9–18.
9. Jay RM. Talonavicular joint arthrodesis and Evans calcaneal osteotomy for treatment of posterior tibial tendon dysfunction. J Foot Ankle Surg 1999 Jul-Aug; 38(4):305.

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